Sirenia Systems | Biomimetic Ocean Engineering

Comparative Sirenian Anatomy

Dugong & Manatee — Layered Anatomical Reconstruction

The Mechanatee uses a hybrid sirenian reference model: musculature from the dugong (Dugong dugon, Domning 1977) mapped onto the vertebral column and fluke geometry of the Florida manatee (Trichechus manatus latirostris). Both species share the same fundamental locomotor architecture — dorso-ventral undulation driven by antagonistic epaxial/hypaxial muscle chains — but diverge in caudal segment count, fluke morphology, and shoulder architecture.

Dugong (Dugong dugon)

Fluke: Lunate (crescent-shaped), cetacean-like. Higher aspect ratio.
Swimming: More specialized, greater endurance. Open-water habitat.
Musculature: More developed hypaxial system. Separate SVL/SVM divisions. "Fluke elevator" tendons present. Greater transverse flexibility.
Source: Domning (1977), Smithsonian Contributions to Zoology No. 226. 57 pages, 54 figures, 2 tables. The most complete published sirenian myology.

Manatee (Trichechus manatus)

Fluke: Spatulate (paddle-shaped). Lower aspect ratio. Thrust via pitching.
Swimming: Less specialized, less endurance. Protected-water habitat.
Musculature: Transversospinalis better developed relative to longissimus. Shorter neural spines, larger metapophyses, longer centra. Less anatomical specialization for swimming — but more maneuverable in restricted waters.
Source: Murie (1872, 1880), Kojeszewski & Fish (2007).

Manatee — Five-Panel Anatomical Layover

Five progressive layers from outer envelope to skeleton. The envelope (panel 1) is regenerated at runtime from the current muscle and skeletal reconstruction. Nervous system routed using comparative cetacean and sirenian neuroanatomy (Reep, Morgane, Marshall, Pabst); musculature follows the dugong-derived Domning (1977) map; skeleton is the real manatee STL.

Mechanatee five-panel anatomical layover: envelope, nervous system, vascular, musculature, skeleton

Generated by manatee_anatomy_layover.py. Hybrid sirenian model — muscles are dugong-derived (Domning 1977), skeleton is manatee.

Dugong — Full-Body Musculature (Domning 1977)

The definitive anatomical reference for sirenian musculature. Skin thickness distribution, lateral dermal muscles, and dorsal superficial/deep layer dissection of Dugong dugon.

Domning (1977), Figures 1–3. Top: Skin thickness along dorsal (D), lateral (L), and ventral (V) midlines (8–18 mm range). Middle: Lateral view — dermal muscles and superficial aponeuroses with CuT, SpC, and platysma divisions. Bottom: Dorsal view — superficial layer (right side), deeper layer with splenius, longissimus capitis, and shoulder muscles removed (left side).

Dugong Caudal Musculature — Progressive Dissection

Anatomical plates from Domning (1977) revealing the layered musculature of the posterior trunk and tail through progressive dissection — from superficial skin muscles down to the deepest vertebral attachments. Each layer informs actuator placement in the Mechanatee.

Dugong caudal musculature — Figures 49 and 50, lateral dissection

Figs. 49 & 50 — Superficial layer: IlT, IntE, LnD, Intr, OAE, RA, CoVe/CoVu, Isc, SVL exposed. Second layer: deep Intr bundles, OAI, TrA, SVL triangular cross-section.

Dugong deep ventral muscles — Figures 51–54

Figs. 51–54 — Deep musculature: SVL, SVM, FH, chevron bones (ch₅–ch₁₂). Pelvic attachments: Isc, RA, CoVe, Intr_d, ReI on lateral and medial pelvis views.

Dissection-to-Actuator Layer Mapping

Layer	Biological Muscles (Domning Figs. 49–54)	Mechanatee Actuator Role
1 — Superficial	Cutaneus trunci (CuT), intercostales externi (IntE), obliquus abd. ext. (OAE)	Skin-mounted strain sensors; no active actuation
2 — Intermediate	Longissimus dorsi (LnD), rectus abdominis (RA), obliquus abd. int. (OAI), SVL	Primary dorsal/ventral antagonistic actuator pairs (HASEL or SMA)
3 — Deep	SVL+SVM (deep), flexor haemalis (FH), Intr_d, transversus abdominis (TrA)	Secondary actuators for fine amplitude and lateral steering
4 — Pelvic Origin	Ischiococcygeus (Isc), coccygeus ventralis/dorsalis, retractor ischii (ReI)	Proximal anchor actuators; baseline tail tension and posture

3D Reconstruction

Musculoskeletal System — Complete Digital Reconstruction

132 individually modeled muscles, 46 skeletal elements, and 4 tissue types mapped from Domning (1977) dugong dissection and Reidenberg (2018) manatee plates onto a unified 3D musculoskeletal framework.

132

Muscles Modeled

46

Skeletal Elements

4

Tissue Types

11

Functional Groups

25,200

Mesh Points

50

Vertebrae

Full musculoskeletal reconstruction — 132 muscles, 46 bones, 4 tissue types

Full musculoskeletal reconstruction. Semi-transparent envelope with color-coded functional muscle groups. Epaxial (red), hypaxial (blue), lateral (cyan), abdominal (green), shoulder/back (orange), flipper/pectoral (purple), superficial/subcutaneous (pink).

Shoulder & back detail. Epaxial chain (LnD, IlT, transversospinalis) with rib cage, scapular muscles, and neural spine attachments. Green: abdominal core. Pink: superficial sheet (CuT). The full dorsal extensor system that drives the upstroke.

Flipper & pectoral detail. 30 forelimb muscles (15 per side) including extrinsic shoulder group, intrinsic arm/forearm, and hand musculature. Position control system — not propulsion (Reidenberg 2018).

Dorsal view showing bilateral musculature and nerve/vessel pathways

Dorsal view. Bilateral symmetry of the muscle system with nerve/vessel pathways (white traces) running between the pectoral flippers. 50 vertebrae visible through the semi-transparent envelope.

Posterior view of musculoskeletal system with muscle group toggles

Posterior (caudal) view. Frontal cross-section perspective showing the concentric layering of muscle groups around the vertebral column — the same architecture that the HASEL actuator array replicates.

Exterior Geometry & Swim Sequence

Textured beauty render. Dragon Skin silicone outer body with Sharklet-inspired antifouling microtexture. Visual indistinguishability target: juvenile manatee at 5 m in turbid water.

Eight-frame swim sequence. Body posture sampled across one full dorso-ventral undulation cycle. Travelling-wave kinematics with quadratic amplitude envelope.

Orthographic multi-view. Side, top, front, and 3/4 perspectives.

Domning (1977) — Smithsonian Contributions to Zoology No. 226

Sirenian Muscle Encyclopedia

Complete myological reference for the order Sirenia, derived from Domning's dugong dissection and cross-referenced with Murie (1872, 1880) manatee descriptions. 57 pages, 54 figures, 2 tables. Every muscle mapped to its Mechanatee actuator equivalent.

Anatomy Source Caveat — Read First

Muscle nomenclature and fiber descriptions below follow the dugong (Dugong dugon) dissection by Domning (1977). The skeleton and fluke in the Mechanatee are manatee (Trichechus manatus). This is a deliberate, disclosed hybrid — no equivalent peer-reviewed manatee musculature dissection of comparable detail exists. Quantifying where dugong→manatee homology breaks down is itself part of the research roadmap.

Swimming Muscles — The Propulsive System

"Sirenians can, apparently by contraction of diagonally opposite sacrococcygeus ventralis lateralis and longissimus muscles, oscillate their tail fins about the long axis of their bodies." — Domning (1977), p. 29. Forward motion is initiated by an upstroke.

Epaxial System — Upstroke (Dorsal Extension)

The epaxial muscles of the Sirenia are characterized by extensive fusion, obscuring most of the divisions easily observed in land mammals. The extreme shortening of the neck, loss of hind limbs, and fusion of trunk and tail regions creates a single continuous epaxial muscle mass from occiput to tail tip.

LnD

M. longissimus dorsi

Principal epaxial mass. Continuous unit from atlas to end of tail. Fleshy and tendinous on transverse process of atlas; at C₆ attachment fused with iliocostalis. Origin: fleshy from dorsal sides of transverse processes, first thoracic back into flukes, dorsolateral sides of neural arches from T₁ back, and dorsal sides of all ribs inside their angles. Inserts via separate round tendons to aftermost caudals.

Upstroke — Primary

SeC

M. semispinalis capitis

Short, shallow longitudinal cleft on surface of muscle at about atlas level. Posteriorly continuous with undifferentiated epaxial mass. Undifferentiated short muscle fascicles and tendons spanning ≤4 vertebrae. Fleshy attachments to dorsal side of transverse process of atlas.

Upstroke — Medial

IlT

M. iliocostalis thoracis

Least developed of the epaxial systems. Single unit, no pelvis attachment. Long narrow band, widest (5.5 cm) at 9th rib. Lateral to longissimus, covering ribs just distal to their angles. Pinnate fiber bundles with overlapping tendons. Tendons with fibers insert on posterolateral sides of ribs, 4–5 forward of origin.

Upstroke — Lateral

Hypaxial System — Downstroke (Ventral Flexion)

The large epaxial and hypaxial locomotor muscles are supplemented in the dugong by an unusual development of the subcutaneous muscles (cutaneus trunci). This consists of a thick mass on the underside of the tail, connected to the ischium by a separate "ischiococcygeus," continuous with the abdominal sheet. "Its action is clearly to flex the tail." — Domning (1977), p. 29.

SVL

Sacrococcygeus ventralis lateralis

Primary downstroke muscle. Broad, triangular cross-section with aponeurosis. From caudal transverse process tips and ribs 17–19. Deep to cutaneus trunci. Originates from ventrolateral processes of caudal vertebrae.

Downstroke — Primary

SVM

Sacrococcygeus ventralis medialis

Deep to SVL, from lateral sides of chevron bones. More oblique fiber arrangement. Works in concert with SVL for powerful ventral flexion.

Downstroke — Deep

FH

M. flexor haemalis

Along chevron bone tips, increasing posteriorly. Flexes the tail ventrally (downstroke). Lever arm of ventral caudal flexor system. Attaches to hemal arches of caudal vertebrae.

Downstroke — Lever

Isc

M. ischiococcygeus

Fleshy from ventromedial edge of ischium and distal end of ilium. Runs medially and posteroventrally parallel to pelvis. In manatee attached to first two chevron bones. Extends from ischium (pelvis) to tail via deep aponeurosis.

Downstroke — Pelvic

CuT

Cutaneus trunci

Subcutaneous sheet from axilla to fluke base. Thick caudal mass unique to sirenians. "Its action is clearly to flex the tail" (Domning 1977). In the manatee, the caudal extension is much less developed. Dorsal fibers sweep up to mingle with auricularis profundus.

Downstroke Assist

RA

M. rectus abdominis

Ventral support along underside, sternum to ischium. Flexes spine for downstroke assistance. Broad, flat muscle along ventral midline providing sustained ventral flexion force.

Downstroke Assist

Lateral System — Steering & Yaw Control

SDL

Sacrococcygeus dorsalis lateralis

Lateral division of epaxial mass at transverse process tips. Produces lateral flexion of caudal peduncle for yaw steering. Works with Intr for turning maneuvers.

Lateral — Yaw

Intr

Intertransversarius coccygeus

Long fusiform muscle, 2nd lumbar to tail tip. Deep bundles (Intr_d) between individual transverse processes for fine tail adjustments. Both superficial and deep divisions present. Essential for precise low-speed maneuvering.

Fine Control

LaD

M. latissimus dorsi

Broad, superficial. Wraps around dorsal side, fused posteriorly with CuT. Swimming direction control and lateral trunk stabilization.

Structural

Core Stability & Abdominal System

OAI

Obliquus abdominis internus

Trunk rotation and spine stabilization. Partially wraps tail. Deep to OAE.

Stabilization

OAE

Obliquus abdominis externus

Pinnate segments on ribs 3–19, directed posteroventrally. Core compression.

Stabilization

TrA

Transversus abdominis

Deepest abdominal layer. Compresses core, stabilizes spine. Ribs 3–19 to pelvis.

Stabilization

Forelimb Musculature — Position Control, Not Propulsion

30 forelimb muscles (15 per side). Per Reidenberg (2018, Encyclopedia of Marine Mammals): "These muscles are used by sirenians for slow ambulation along the riverbed, but are not particularly strong… reduced in cetaceans as they use the flippers primarily for adjusting swimming position and braking, but not propulsion."

Trp / LaD / Rh

Extrinsic Dorsal Group

Trapezius, latissimus dorsi, rhomboideus. Dorsal thorax to scapula/humerus. In dugong, serratus magnus is divided into separate anterior/posterior parts.

Shoulder

PMa / PMi / D

Extrinsic Ventral + Shoulder

Pectoralis major/minor, deltoid, supraspinatus, infraspinatus, teres major, subscapularis. Manatee bicipital groove absent; no separate heads.

Shoulder

ECR / FCR / FDP

Forearm & Hand

Extensors (ECR, ECU, EDC, EDQ), flexors (FCR, FCU, FDP, FDS), pronator teres, palmaris longus, interossei, AbD V. Digits II–V present in both species.

Flipper

Structural & Sensory Elements

Chevron Bones (ch)

V-shaped bones on ventral side of caudal vertebrae. Protect blood vessels, serve as FH and SVM attachment points. 9–13 per tail.

Caudal Vertebrae (Ca)

24–29 vertebrae. Central axis of movement. Ball-and-socket facet joints for controlled pendulum-like oscillation.

Diaphragm

Unusually large, muscular, and horizontally oriented in sirenians. Functions in buoyancy control as well as respiration. The manatee diaphragm is the most horizontally positioned of any mammal.

Complete Muscle Abbreviation Index

Abbrev.	Muscle	Group	Domning Fig.
LnD	Longissimus dorsi	Upstroke	3, 22–24, 49–52
IlT	Iliocostalis thoracis	Upstroke	3, 22–24, 49
SeC	Semispinalis capitis	Upstroke	3, 12–15, 20–24
FH	Flexor haemalis	Downstroke	51
SVL	Sacrococcygeus vent. lat.	Downstroke	49–52
SVM	Sacrococcygeus vent. med.	Downstroke	51
Isc	Ischiococcygeus	Downstroke	52–54

Abbrev.	Muscle	Group	Domning Fig.
RA	Rectus abdominis	Assist	23, 24, 49–53
CuT	Cutaneus trunci	Assist	2, 3, 49–52
OAI	Obliquus abd. internus	Stabilization	34, 50, 52
TrA	Transversus abdominis	Stabilization	50–54
Intr	Intertransversarius	Fine control	3, 49–53
LaD	Latissimus dorsi	Structural	22, 32, 46–47
ReI	Retractor ischii	Structural	53–54

Source: Domning, D.P. (1977). "Observations on the myology of Dugong dugon (Müller)." Smithsonian Contributions to Zoology, No. 226. Cross-referenced with Murie (1872, 1880) manatee descriptions and Reidenberg (2018) Encyclopedia of Marine Mammals.

Ocean Engineering Mathematics

The Physics of Biomimetic Underwater Locomotion

From Navier-Stokes to Lighthill, from Strouhal to coupled neural oscillators — every equation governing the Mechanatee's hydrodynamic performance, derived from first principles and validated against biological kinematic data.

Swimming Kinematics — Progressive Wave Model

Manatee swimming is classified as subcarangiform: dorso-ventral undulation propagating as a traveling wave from peduncle to fluke tip. Kinematic parameters from Kojeszewski & Fish (2007).

Tail Displacement

y(x, t) = A(x) · sin(2πft − 2πx/λ)

Amplitude Envelope (Quadratic Growth)

A(s) = A_tip · (s / L_tail)²

A/BL = 0.22 peak-to-peak (K&F07). A_tip = 0.275 m single-side. L_tail ≈ 1.04 m (26 segments × 40 mm). Quadratic envelope matches biological growth.

Frequency–Speed Relationship

f(U) = 0.24 + 0.22U [Hz]

Biological cruise = 0.5 m/s → f = 0.35 Hz. Design cruise = 0.8 m/s → f = 0.416 Hz, T = 2.40 s.

Wave Speed

V_wave = 0.51 + 1.09U [m/s]

Always exceeds body speed — maintaining thrust-generating phase lag.

Segmental Peak Acceleration

a(x, t) = −A(x) · ω² · sin(kx − ωt)

Drives inertial loads on actuators. ω = 2πf, k = 2π/λ.

Joint Angle

θ_j(t) = arctan[(Δz_j+1 − Δz_j) / Δx_j]

Traveling wave propagation through one complete swim cycle.

Deformation envelope showing quadratic amplitude growth along caudal spine.

0.275 m

Fluke Tip Amplitude

3.32 m

Wavelength (cruise)

26

Caudal Segments

6 per seg

Actuators

Re ~ 10⁶

Reynolds Number

St ≈ 0.14

Strouhal Number

Swim cycle. Dorso-ventral undulation at design cruise (0.8 m/s, f ≈ 0.42 Hz).

CFD flow. Velocity field, streamlines, and reverse Kármán vortex street. Panel-method + boundary layer + Theodorsen unsteady-lift prediction.

Fluid Dynamics

Hydrodynamic Force Analysis

Thrust, drag, and propulsive efficiency derived from Buckingham Pi analysis, elongated-body theory (Lighthill 1971), and Strouhal optimization.

Dimensionless Groups & Flow Regime

Reynolds Number

Re = ρUL / μ

ρ = 1025 kg/m³, μ = 1.08×10⁻³ Pa·s (seawater @ 25°C). Re = 2.37×10⁵ (0.1 m/s) → 3.57×10⁶ (1.5 m/s). Turbulent regime.

Strouhal Number

St = fA / U

At cruise: St = 0.416 × 0.275 / 0.8 = 0.143. Below the 0.20–0.40 optimal band (Taylor, Nudds & Thomas 2003). Manatees are low-St swimmers.

Reduced Frequency

k = πfc / U

Quantifies unsteady effects on the fluke; c = 0.28 m (fluke chord).

Thrust, Drag & Navier-Stokes

Friction Drag (ITTC 1957)

F_D = ½ρU²S_wetC_D

C_D = 0.075 / (log₁₀Re − 2)² ≈ 0.0065 at cruise. S_wet = 2.2 m². F_D ≈ 4.7 N.

Lighthill Thrust (Elongated Body Theory)

T = ½m_a(L) · w(L,t)² − recoil terms

m_a(L) = ρπb² = 340 kg/m. At cruise: T ≈ 24.1 N vs. drag F_D ≈ 4.7 N.

Added Mass (Elliptical Cross-Section)

m_a(x) = ρ · π · b(x)²

b(x) = local half-height. Varies from ~0.25 m mid-body to ~0.003 m at fluke trailing edge.

Total Bending Moment at Joint j

M_total,j = ∑_k=j+1^N (m_k + m_a,k) · a_k · r_jk

Peak M_total ≈ 122.4 N·m at proximal caudal joint (x = 1.456 m).

Strouhal sweep: propulsive efficiency vs. St. Mechanatee at St ≈ 0.14.

Annotated flow field with thrust, drag, and reactive force components.

Strouhal number comparison: Mechanatee vs cetaceans, fish, eels, pinnipeds

Mechanatee in the swimmer design space. Operating at St ≈ 0.14 — below the canonical 0.20–0.40 efficiency band. The low-Strouhal niche of slow, quiet, vegetated-water survey.

Force Vector Analysis

Distributed reactive & resistive forces during dorso-ventral tail undulation.

Per-segment force decomposition: inertial, pressure, and net thrust.

Lift generated through active fluke pitch modulation — SMA-driven real-time pitch.

Total bending moment: inertial + hydrodynamic components across speed range.

Central Pattern Generator — Spinal Drive Architecture

The tail is driven by a network of coupled neural oscillators — not an open-loop sine wave. Same architecture validated by Ijspeert et al. on Salamandra robotica, adapted for sirenian dorso-ventral undulation.

Segmental Phase Oscillator (Ijspeert 2008)

θ̇_i = 2πν + Σ_j w_ij r_j sin(θ_j − θ_i − φ_ij)

θ_i = phase at vertebra i; ν = global drive frequency; φ_ij = inter-segmental phase bias (sets wavelength); w_ij = nearest-neighbor coupling weight.

Amplitude Dynamics

r̈_i = a (a/4 (R_i − r_i) − ṙ_i)

R_i = target amplitude (sets envelope).

Phase → Joint Angle (Antagonistic Pair)

θ_joint,i(t) = r_i(t) · cos(θ_i(t)) · A_env(s_i/L_tail)

Dorsal (epaxial) fires for θ_i ∈ [−π/2, π/2]; ventral (hypaxial) fires for the antagonistic half-cycle.

Drive-Signal → Behavior

Behavior	Drive	Kinematics
Station-hold	ν₀ = 0	Tail flaccid, trimmed
Cruise (0.8 m/s)	ν₀ = 0.42 Hz	Symmetric DV, peak η_p
Slow turn	Δν_L/R ≠ 0	Asymmetric amplitude
Surface/dive	ΔR_U/D ≠ 0	DC offset on antagonists
Reverse	φ_ij → −φ_ij	Head-ward wave

Phase-lagged joint-angle profile across 26 caudal segments — the kinematic output of the coupled-oscillator network.

Why a CPG, Not a Lookup Table

Robustness: Re-entrains to perturbations within one cycle.

Smooth transitions: Cruise → sprint → station-hold → reverse all expressed as drive-signal changes.

Biological fidelity: Same equations describe lamprey, salamander, dogfish, and (by homology) sirenian spinal locomotor networks.

Efficiency & Cost of Transport

Froude Efficiency

η_F = U / V_wave = 0.8 / 1.382 ≈ 0.58

Cost of Transport

COT = P_total / (mgU) [J/(m·kg)]

Speed	Thrust	Power	η_prop	COT
0.3 m/s	13.2 N	0.15 W	0.72	0.0010
0.5 m/s	17.3 N	0.64 W	0.75	0.0026
0.8 m/s	24.1 N	2.49 W	0.79	0.0065
1.0 m/s	29.5 N	4.25 W	0.81	0.0100
1.3 m/s	39.0 N	9.22 W	0.76	0.0173
1.5 m/s	45.9 N	13.8 W	0.73	0.0231

8-Hour Mission Battery

E = 125 W × 8 h = 1000 Wh → 5.0 kg Li-ion (200 Wh/kg)

Froude efficiency and cost of transport across operating speed range.

Velocity and acceleration profiles — peak η_p at 0.95 m/s matches biological data.

Comparative biomimetic flow visualization across four species

CFD Quad Chart — Biomimetic Wake Comparison

(a) Tuna / Thunniform: Attached boundary layer, narrow wake, high-speed cruising.
(b) Squid / Jet: Pulsed vortex rings, high accel, low efficiency.
(c) Whale / Cetacean fluke: Dorso-ventral pitching hydrofoil, reverse Kármán street.
(d) Eel / Anguilliform: Full-body undulation with distributed thrust.
Mechanatee operates between (a) and (c) — subcarangiform with cetacean-style fluke.

The Low-Strouhal Advantage

St ≈ 0.14–0.28 vs. 0.3–0.4 for dolphins. Spatulate fluke generates thrust through pitching rather than pure heaving. Quieter propulsion, less turbidity — ideal for coastal/estuarine operations where the vehicle must be invisible to both wildlife and instrumentation.

Interactive Models

Digital Twin & 3D Visualization

Interactive exploration of the Mechanatee musculoskeletal system — toggle individual muscle groups, isolate epaxial vs. hypaxial chains, and examine vertebral geometry.

Epaxial System (Upstroke)

M. longissimus dorsi: atlas to tail tip. Transversospinalis and IlT provide medial/lateral dorsal force. Transmits distally through subdermal connective tissue sheath (Pabst 1996).

Hypaxial System (Downstroke)

SVL primary, with SVM, flexor haemalis (chevron bones), rectus abdominis providing ventral flexion. CuT caudal mass unique to sirenians adds subcutaneous tail flexion.

Lateral System (Steering)

Intertransversarius and SDL produce lateral bending for yaw control. Transverse process tips provide precise slow-speed maneuvering in shallow-water environments.

Spine curvature — segment lengths inform inter-disk spacing and actuator mounting.

60-point spine within mesh hull. Virtual mass coefficients from slender-body theory.

Mesh & Spine Registration

25,200-point triangulated exterior mesh with embedded 60-point spine centerline from biological CT data. 26 caudal vertebral disks modeled as elliptical cross-sections (~3.5 cm × 2.5 cm) in PA12 nylon, with ball-and-socket joints allowing ±15° dorso-ventral and ±10° lateral articulation.

Hardware & Outreach

Prototypes, Fieldwork & Press

10 prototype iterations over 2.5 years — from servo-pulley mechanisms to biomimetic color-coded muscle layups on 3D-printed vertebral spines. Real manatee skeletal geometry from CT/3D scanning informs every disk, every joint, every actuator placement.

Prototype 9 — top view with color-coded muscle groups on articulated spine

Prototype 9 — Muscle-Mapped Spine (top view). Color-coded silicone muscle groups layered onto 3D-printed PA12 vertebrae. Each color corresponds to a functional muscle group from the Domning (1977) dissection: epaxial (red), hypaxial (blue), lateral (green/cyan), abdominal (yellow).

Prototype 9 — lateral view of color-coded muscle model mounted on wall

Prototype 9 — Lateral View. Physical musculoskeletal model with antagonistic muscle pairs visible. The same architecture that the digital twin replicates — built by hand to validate actuator placement geometry.

3D-printed vertebrae with intervertebral disks and hydraulic tubing

Vertebral Components. PA12 nylon vertebrae with elliptical intervertebral disks (yellow) and hydraulic routing tubing. Ball-and-socket joints allow ±15° dorso-ventral and ±10° lateral articulation.

Full articulated spine prototype with measurement tape

Full Articulated Spine — P9. 26 caudal vertebral segments at ~40 mm spacing. Total tail length matches biological measurement (1.04 m). Most biomimetic prototype to date.

Earlier Iterations & Electronics

Prototype 3 — articulated tail with SMA wires

Prototype 3 — SMA Wire Tail. Shape-memory alloy actuated segments with Dyneema cable tendons. First prototype with antagonistic actuation.

Prototype 3 electronics — breadboard, servo, microcontroller inside hull

P3 Electronics Bay. Breadboard prototyping inside the pressure hull — servo drivers, microcontroller, and power regulation for propulsion testing.

Fieldwork & Outreach

Haylie Garman and Wyatt Amarosa presenting the Mechanatee at Florida Tech STEM Kids Day

STEM Kids Day — Florida Tech. Haylie Garman and Wyatt Amarosa demonstrating the Mechanatee prototype and research to the next generation of engineers.

Seagrass respiration — oxygen bubbles on blades in manatee habitat

Seagrass Respiration. Oxygen bubbles on seagrass blades in Florida manatee habitat — the ecosystem the Mechanatee is designed to survey without disturbing.

Press Coverage

Florida Today (March 23, 2025) — Front Page: “Ecological Espionage — Florida Tech students build robotic manatee to study species in wild.”

Skeletal 3D Scanning — Acknowledgment

The real manatee skeletal geometry used in this project was 3D scanned with permission from Dr. Beth Brady of Save the Manatee Club, who holds a Florida Fish & Wildlife Conservation Commission (FWC) education permit. The scanned skeleton provides the ground-truth vertebral geometry, rib spacing, and flipper bone structure that inform all digital twin and prototype dimensions.

References & Attribution

Key References

Domning (1977)	"Observations on the myology of Dugong dugon (Müller)." Smithsonian Contributions to Zoology, No. 226. Primary sirenian myology reference — 57 pp., 54 figs.
Murie (1872, 1880)	"On the Form and Structure of the Manatee." Trans. Zoological Society of London. First comprehensive manatee anatomy.
Reidenberg (2018)	"Musculature" in Encyclopedia of Marine Mammals, 3rd ed., pp. 622–625. Forelimb functional anatomy.
Kojeszewski & Fish (2007)	"Swimming kinematics of the Florida manatee." J. Exp. Biology 210, 2411–2418. All kinematic regressions.
Lighthill (1971)	Large-amplitude elongated-body theory. Foundation for reactive thrust calculations.
Taylor, Nudds & Thomas (2003)	Flying & swimming animals cruise at Strouhal tuned for high power efficiency. St = 0.20–0.40.
Ijspeert (2008)	"Central pattern generators for locomotion control." Neural Networks 21(4):642–653.
Pabst (1996)	Subdermal connective tissue sheath in cetacean and sirenian swimming mechanics.
Hartman (1971)	"Behavior and Ecology of the Florida Manatee." Ph.D. dissertation, Cornell. Locomotor behavior baseline.
Slijper (1946)	Comparative biologic-anatomical investigations on the vertebral column and spinal musculature of mammals.

Contact

Haylie Garman — Principal Investigator, Marine Biologist, Data Analyst & Ocean Engineer

Sirenia Systems · FIT Alumni 2025

10 prototype iterations · 2.5 years of hydrodynamic testing · 132 modeled muscles

Engineering the Sirenian Musculoskeletal System

Dugong & Manatee — Layered Anatomical Reconstruction

Manatee — Five-Panel Anatomical Layover

Dugong — Full-Body Musculature (Domning 1977)

Dugong Caudal Musculature — Progressive Dissection

Musculoskeletal System — Complete Digital Reconstruction

Exterior Geometry & Swim Sequence

Sirenian Muscle Encyclopedia

Swimming Muscles — The Propulsive System

M. longissimus dorsi

M. semispinalis capitis

M. iliocostalis thoracis

Sacrococcygeus ventralis lateralis

Sacrococcygeus ventralis medialis

M. flexor haemalis

M. ischiococcygeus

Cutaneus trunci

M. rectus abdominis

Sacrococcygeus dorsalis lateralis

Intertransversarius coccygeus

M. latissimus dorsi

Obliquus abdominis internus

Obliquus abdominis externus

Transversus abdominis

Extrinsic Dorsal Group

Extrinsic Ventral + Shoulder

Forearm & Hand

Chevron Bones (ch)

Caudal Vertebrae (Ca)

Diaphragm

Complete Muscle Abbreviation Index

The Physics of Biomimetic Underwater Locomotion

Swimming Kinematics — Progressive Wave Model

Hydrodynamic Force Analysis

Dimensionless Groups & Flow Regime

Thrust, Drag & Navier-Stokes

Force Vector Analysis

Central Pattern Generator — Spinal Drive Architecture

Drive-Signal → Behavior

Efficiency & Cost of Transport

Digital Twin & 3D Visualization

Epaxial System (Upstroke)

Hypaxial System (Downstroke)

Lateral System (Steering)

Mesh & Spine Registration

Prototypes, Fieldwork & Press

Earlier Iterations & Electronics

Fieldwork & Outreach

Key References

Contact

Engineering the
Sirenian Musculoskeletal
System